In a motor vehicle, traditional turn signal cancellation is achieved by a mechanism that is imbedded into the vehicle steering column. Initial activation is by hand movement of the turn signal stalk on the left side of the steering column corresponding to the direction of intent. From that point, automatic cancellation is achieved via a ratchet or latch mechanism that is initiated with a physical turning of the steering wheel. When the steering wheel is turned past a designed-in arc angle in the direction of the intended turn, and subsequently returned, a mechanism is tripped to reset the turn signal to the off position. These pre-determined arc angles are designed by the motor vehicle manufacturer and are fixed angle points within the steering column. This is the only means of automatic cancellation of the turn signal function. The turn signal on a vehicle remains active until either manually disabled by the driver or the steering wheel is turned a predetermined amount and returned.
The manual means of turn signal shut off is one of two varieties: one, where the column stalk is physically moved by hand from the turn-signal-on position to the off position by the vehicle operator. The second means is where the vehicle operator initially intends to perform a “lane change”, thereby moving the column stalk from the off position to an intermediate position between turn signal on and turn signal off. This lane change position will hold the turn signal function on as long as the stalk is hand held in that position. Upon hand removal from the stalk, the turn signal is then shut off. This mode is independent of the steering wheel position or movement.
The problem with this art is that the automatic cancel feature responds to steering wheel rotation only, without regard to any other vital vehicle factors related to the execution of a turn. As a result of this information and intelligence deficiency, a turn signal left-on condition is likely and the driver may be unaware of this condition for an extended period of time while driving. Additionally, any degree of normal dither motion of the steering wheel to steer the vehicle through a turn and while the turn signal is on may cause an unintended shut off of the turn signal prior to the actual completion of the intended turn. Still other conditions may exist where automatic turn signal shut off is inappropriate or non-existent. These conditions can create situations while driving that are a nuisance or are a danger.
Prior art systems have attempted to deal with only one aspect of these shortcomings, that is, the turn signal unintentionally left on. The remedies have mostly used fixed time or fixed distance values to effect a driver alert warning of some form. If time or distance are used to automatically shut off the turn signal, then added complexity of the steering column mechanism would be required in the form of an electromechanical actuator to physically move the turn signal stalk to the center-off position. Both of these remedies add undue complexity and cost to the existing system.
What is needed, therefore, is an improvement to the turn signal system of a vehicle that takes into account many other dynamic factors of the vehicle when a turn is executed for greater turn signal control accuracy, as well as a method that simplifies the current state of the art.